Showy Milkweed Experiment

The Tree of Life Nursery we visited 2 weekends ago had a different type of native milkweed, the showy milkweed, Asclepias Speciosa. Unlike narrow leaf milkweeds I’ve been feeding the caterpillars, these have big leaves, probably 5 times the size of the narrow leaves. I fed one leaf to a bigger caterpillar (instar 4) and it ate it up. But when I fed it to a 2 instar caterpillar, it oozed green, liquified, curled up and died. So it was going to be an interesting experiment when the monarch butterfly laid 9 eggs on 4 showy milkweed plants. Instead of bringing in the eggs inside the house, I put them in a large butterfly cage and left it outside. The cage would protect the eggs from tachinid flies laying eggs and other predatory bugs (spiders!). The eggs have hatched and so far as 2nd instar caterpillars, they are doing well eating the big showy milkweeds. I wonder if switching milkweed types when they are young causes problems.